1. Field of the Invention
The present invention relates to ink ribbon cassettes and protectors for use in printers.
2. Description of the Prior Art
It is conventional to use ink ribbon cassettes, which house an endless ink ribbon, in printers. The cassette is mounted on the printer carriage, and is easily installed without smearing the hands of the operator and the parts of the printer. Such an ink ribbon cassette is shown in U.S. Pat. No. 4,676,681 which is incorporated herein by reference, and which shows projections or pins 7a, 7b and holders 9a, 9b for detachably mounting a ribbon protector 10 which has oblong holes 10a, 10b that are inserted over pins 7a, 7b. Pin 7a is longer than the distance between the surface of ribbon guide arm 2a and holder 9a so the oblong hole 10a of protector 10 cannot fall off the pin 7a. Similarly, pin 7b is longer than the distance between the surface of ribbon guide arm 2b and the holder 9b so the oblong hole 10b of at the other end of protector 10 cannot fall off the pin 7b.
Another example of a ribbon cassette and protector is shown in U.S. Pat. No. 4,383,775 wherein the ribbon protector is mounted on the cassette by fixing it in slits in the ink ribbon cassette or by bonding it to the ink ribbon cassette. U.S. Pat. No. 4,383,775 is also incorporated herein by reference.
If the ribbon protector is fixed to the ink ribbon cassette, it cannot move between the ink ribbon and the paper sheet being printed upon, and therefore it has to be positioned very accurately, which is time-consuming and laborious. Also, ribbon protectors which are fixed to the cassette cannot be easily replaced with a new protector.